1. Field of the Invention
The invention relates to a sewer pipe rehabilitation process whereby a plurality of inner liners made of thermoplastics is inserted into a sewer pipe, closing off any incoming house drain inlets, and is then connected to said house drain inlets by a method involving the creation of a through-hole theretoward in that area of the plastic piping which closes off the house drain inlet. The through-hole is at least the size of the projection of the cross-section of the house drain pipe. A saddle-type branch fitting comprising a pipe segment member and a pipe socket integral therewith and outwardly extending therefrom is positioned in the closed-off area so that the pipe socket will project into the house drain inlet via said through-hole. The pipe segment member is then secured to the plastic pipe. A sleeve with exterior sealing elements is inserted into the incoming house drain inlet so that one end portion of said sleeve is placed tightly against the interior wall of the house drain pipe while its other end portion is placed tightly against the interior wall of the pipe socket extending from said saddle-type branch fitting. The invention further relates to a device and a manipulator for carrying out said process.
2. Description of the Prior Art
The rehabilitation of sewer pipes is becoming increasingly important, both for technical reasons and as a result of a growing environmental awareness. Diverse attempts are known in the art to provide mechanized processes and devices for the rehabilitation of pipelines. Such mechanized solutions are of universal interest, given that working conditions are already difficult in walk-through pipes, while in the rehabilitation of non-walk-through pipes they are such as to make mechanized aid altogether indispensable. A particular difficulty lies in the rehabilitation of pipelines near house drains terminating in the sewer.
A prior process and apparatus for the rehabilitation of sewer pipes is known from DE 39 31 616 C 2. According to this publication, plastic pipes made of a thermoplastic material are first inserted into a sewer pipe. Inside the sewer pipe thus lined. A deformation member is then positioned with the aid of a carriage before an incoming house drain inlet, which is initially closed off by the wall of the plastic piping. The deformation member is then pressed against the wall of the plastic pipe from the inside of the sewer pipe, and is heated so as raise the temperature of the plastic pipe until the latter becomes plasticized. The deformation member is then forced into the house drain inlet, forming a socket of that area of the plastic pipe material which had initially closed off the house drain inlet. This socket is then trimmed, and the deformation member is retracted towards the carriage. No special sealing is provided in the annular space between the plastic pipe and the house drain inlet.
The disadvantages of such a solution include the fact that, inter alia, the process can only be used with thermoplastic material, while the geometry of the socket thus formed cannot be exactly defined in advance. Variations will be found both in the wall thickness, and hence the strength, as well as in the length of the socket. Moreover, there is virtually no sealing between the socket and the house drain inlet. This is a result of the fact that the junction is fabricated in-situ, i.e., subject to operating conditions and procedures which cannot be controlled with any degree of precision. In addition, this process requires the center of the house drain inlet to be determined with particular accuracy, since a satisfactory result can only be obtained if the socket is properly centered. Another problem with this solution lies in the fairly large equipment dimensions involved, making the apparatus suitable only for use in sewer lines of appropriately large diameter.
EP 0 640 727 A1 discloses a process and apparatus for connecting and sealing a lateral inlet or house sewer to a main sewer pipe to be rehabilitated with a thermoplastic inner liner. With this system a thermoplastic pipe socket having a flange and an outwardly projecting cylindrical portion integral therewith which extends into the lateral inlet is thermally fused with the inner liner. For this process a cylindrical insert or sleeve, having exterior sealing strips on its end portions, is inserted with the aid of a heatable expander device positioned therein. Once the cylindrical portion and the sleeve have been heated to the point of softening, they are expanded by the expander device so as to be placed firmly against the lateral inlet, with the front sealing strips engaging the interior wall of the lateral inlet and the rear sealing strips engaging the interior wall of the cylindrical portion of the pipe socket, whereupon the expander device is removed.
A drawback of this process lies in the fact that the thermal fusion process whereby the plastic pipe socket is joined to the inner liner may produce questionable and unreliable results in the presence of moisture and in difficult-to-clean mounting locations. Moreover, the strain on the junction due to thermally induced shear stress and other effects will be so intense as to become virtually unmanageable with plastic sockets and saddle-type fittings in a reasonable wall gauge range, particularly if significant restrictions in cross-sectional area are to be avoided.